Flying coating head mounted on pivotal beam



y 26, 1966 H. R. J. KNIGHT 3,

FLYING COATING HEAD MOUNTED ON PIVOTAL BEAM Filed March 24, 1965 6 Sheets-Sheet 1 /2 4s 29 I 0 f Q0 94 H 35 I t 494E] Howan/ fiiclmnlril rs s km llf July 26, 1966 H. R. J. KNIGHT 3,262,419

FLYING COATING HEAD MOUNTED ON PIVOTAL BEAM Filed March 24, 1965 6 Sheets-Sheet 2 I t r Howa rc/ Ricl'm vrl Jqme is l klflj l2 '1- y 26, 1966 H. R. J. KNIGHT 3,262,419

FLYING COATING HEAD MOUNTED ON PIVOTAL BEAM Filed March 24, 1965 6 Sheets-$heet 5 29 My Egg.

35 K 50 46 [in -4@ g. y 1 42- 1 we 45k J j, ,/4

Inventor HoWar'J larc/ klqm(s v July 6, 1966 H. R. J. KNIGHT FLYING COATING HEAD MOUNTED ON PIVOTAL BEAM Filed March 24, 1965 6 Sheets-Sheet 4 y 6, 1966 H. R. J. KNIGHT 3,262,419

FLYING COATING HEAD MOUNTED ON PIVOTAL BEAM Filed March 24, 1965 6 Sheets-Sheet 5 Inventor I HGWJ Rmk rl 'ama /7712? y A? 00M 1 3 July 26, 1966 H. R. J. KNIGHT 3,262,419

FLYING COATING HEAD MOUNTED ON PIVOIAL BEAM Filed March 24, 1965 6 Sheets-Sheet 6 /0 [nuenfor By m w United States Patent 3,262,419 FLYING COATING HEAD MOUNTED 0N PIVOTAL BEAM Howard Richard James Knight, Leamington Spa, England, assignor to Carrier Engineering Company Limited, London, England, a corporation of Great Britain Filed Mar. 24, 1965, Ser. No. 442,386 Claims priority, application Great Britain, June 15, 1960, 21,082/ 60 3 Claims. (Cl. 118-7) This application is a continuation-in-part of application Serial No. 117,104, filed June 14, 1961 and now abandoned.

This invention relates to coating machines and in particular to apparatus for spray-painting surfaces of articles, for example surfaces of cars bodies, or sides of refrigerator cabinets, while the articles are moved past a paint spraying device at a constant linear speed.

In one form of known machine for spray-painting the surfaces of articles the articles are moved past a paint spraying device by a conveyor moving at a constant linear speed and the paint spraying device comprises a spray gun which is mounted on a carriage for reciprocation in a plane alongside the path of the articles, the gun being reciprocated along a fixed path. The arrangement is such that the gun completes at least two reciprocations during the painting of a side of an article thus providing two upward and two downward painting strokes during which there is overlapping of paint applied to the surface of the article. It is, however, difiicult to ensure an even coat thickness by this known method because the painting strokes are inclined across the side of the article and it is a main object of the present invention to provide apparatus for effecting spray painting whereby a more even coating thickness is obtained regardless of the number of overlapping coats of paint which are applied.

It is a further object of the invention to reduce the wastage of paint which has been inevitable hitherto, by reducing the amount of overspraying which is necessary before and after the article to provide the required coating on each article.

According to the invention there is provided an apparatus for painting a surface of an article moving in a straight line path at a constant linear speed, comprising means to traverse a spraying device across the surface in a vertical plane parallel to the path of the article alternately in straight line paths which extend beyond opposite edges of the surface being coated, which paths lie on opposite sides of a line at right angles to the path of the article, means changing the inclination of the path of the spraying deviceat the end of each traverse of said device along one of said straight line paths so that in each path a component of the movement of the spray from the spraying device always lies in the same direction as the direction of movement of the article, means maintaining constant the angle at which the spray is directed by the spraying device towards the surface, and so controlling the movement of the article and the spraying device that the increment of forward movement of the article during each traverse of the spraying device is 'a factor of the width of the spray where it impinges on the article surface, thereby producing a uniform coating comprising overlapping bands of paint on said surface.

Preferably said increment of forward movement of the article during each traverse of the spraying device may be one third of the spray width.

Further according to the invention there is provided apparatus for coating an upright surface of an article, comprising a beam supportable for pivotal movement about a horizontal axis intermediate its ends in a vertical plane parallel to the path of a conveyor by which articles Patented July 26, 1966 to be coated are moved in a straight path at a constant linear speed, a carriage mounted on the beam, means for reciprocating the carriage in a straight line path up and down the beam, a coating material spraying device supported on the carriage and arranged to spray coating ma terial on to an upright surface of an article during movement of the article past the spraying device, and beam swinging means including control devices fixed to the beam and operable at the end of each stroke of the carriage to swing the beam about said axis, whereby the spraying device during successive strokes thereof is traversed along straight line paths inclined on opposite sides of a line at right angles to the direction of movement of the articles and in a direction in each path such that a component of the movement of the spraying device always lies in the same direction as the direction of movement of an article being coated. The coating head may thus be said to have a flying motion.

Still further according to the invention the beam swinging means comprises a change-over air cylinder housing a piston, a piston rod connecting the piston to the beam at a position adjacent to one end of the beam, compressed air supply means connected to said cylinder and pneumatic switching devices mounted at the ends of the beam and connected to the compressed air supplying means, each pneumatic switching device being operable when contacted by the carriage at the end of a stroke of the carriage to cause the compressed air supply means to switch over the supply of air to said change-over cylinder thereby causing the beam to swing about its axis.

Stops may be provided which are engageable by the beam to determine the extent of swinging movement of the beam, said stops being adjustable relative one to the other to vary the spacing therebetween according to the linear speed of the conveyor.

In one embodiment of the invention the spraying device includes two spray guns spaced apart in the direction of movement of the article, and control means connected to the spray guns to switch them on and oif separately during the passage ofan article past the guns.

In order that the invention may be more clearly understood, some embodiments thereof will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic representative of apparatus according to the invention and its mode of operation,

FIGURE 2 is a front elevation of part of the apparatus illustrated diagrammatically in FIGURE 1,

FIGURE 3 is a side elevation of the apparatus of FIG- URE 2,

FIGURE 4 illustrates diagrammatically in plan view a modification of the apparatus of FIGURES 2 and 3,

FIGURE 5 is a side elevation of the apparatus of FIG- URES 1 to 3, shown in greater detail,

FIGURE 6 is a section on line VI-VI of FIGURE 5, and

FIGURE 7 illustrates the pneumatic circuit for operation of the apparatus of FIGURES 5 and 6.

In the drawings the same references indicate the same or similar parts.

Referring to FIGURE 1 of the drawings, an article 1, such as a refrigerator cabinet, indicated in broken lines is moved by an overhead conveyor indicated generally at 2, of known construction at a constant linear speed in a straight line path, the article being suspended from the conveyor so that the surfaces of the sides thereof which are to be painted are substantially upright. It is however, to be understood that if desired, the articles can be supported by a conveyor disposed beneath the articles.

Painting is effected by a spray gun 3 of 'known construction, which is supported by a carriage 4 mounted on an endless chain, not shown, which is supported by a beam, also not shown. The carriage 4 is guided for reciprocation lengthwise of the beam and movement of the carriage is effected by an electric motor, not shown. In the drawing the upward path of the gun 3 is indicated by the broken line 5 and the downward path is indicated by the broken line 6 and from the drawing it will be noted that the gun is moved in a vertical plane parallel with the path of the article 1 and that painting is effected alternatively in paths 5, 6 which are inclined on opposite sides of a vertical line in said plane. The direction of movement of the spray gun in each path 5, 6 is such that a component of the movement of the spray gun is always in the same direction as the direction of movement of the article 1.

To permit movement of the gun in the paths 5, 6 the beam is mounted on a pivot 7 supported by brackets, not shown, the position of the pivotal axis being approximately midways between the opposite ends of the stroke of the carriage 4. Beam-swinging means are provided to effect swinging of the beam about the pivotal axis 7, such means being controlled by the carriage 4 as it reaches the opposite ends of its stroke.

The beam-swinging means comprises a change-over air cylinder 8 housing a piston 9 having a piston rod 10 connected thereto and to the beam as indicated by the reference 11. The ends of cylinder 8 are connected by air lines 12, 13 to the outlet ports of a two-way control spool valve 14, of well-known kind which is supplied with air under pressure through a line 15 connected to the inlet port of the valve 14. Air at a pressure of about 80 pounds per square inch is supplied on line 15. The side control ports of the valve 14 are connected by air lines 16, 17 to bottles 18, 19 containing air under pressure and acting as pressure reservoirs so that normally the pressure is equal on both sides of the sliding spool of the valve 14 and lines 16, 17 are respectively connected through non-return valves 20, 21 to low pressure lines 22, 23 which admit to lines 16, 17 air at a low pressure of about 12 pounds per square inch. Lines 16, 17 are respectively connected through air lines 24, 25 with air cylinders 28, 29 provided with pistons 30, 31 and stems 32, 33 which project into the path of the carriage 4. Relief valves 26 and 27 prevent any accidental build-up of pressure on the lines 16 and 17.

The air cylinders 28, 29 cushion the carriage at the opposite ends of the stroke thereof and engagement of the carriage with one or other of the stems 32, 33 effects operation of valve 14 to control swinging of the beam about the pivotal axis 7. Thus it will be understood that the carriage controls swinging of the beam at the end of each upward and each downward stroke of the carriage.

The beam carries abutments which engage with one or other of a pair of stops 34, 35 which are adjustable relative one to the other to vary the spacing therebetween according to the linear speed of the conveyor 2. The stops are mounted on a support 36 provided with graduation marks 37 indicative of conveyor speeds.

In FIGURE 1 the carriage 4 is just about to strike the stem 32 and the engagement of the carriage with this stem depresses the piston 30 and causes a pressure surge or impulse along the lines 24 and 16. This impulse moves the spool in the valve 14. so that high pressure air is switched from line 12 to line 13 and the piston rod 10 is retracted into the cylinder 8 until the bottom of the beam engages the stop 35. The spool of the valve 14 remains in its new position because, after the surge has died away, the pressure is equal on both lines 16 and 17.

Similarly when the carriage 4 strikes the stem 33 the pressure surge along lines 25 and 17 caused by depression of the piston 31 moves the spool of the valve 14 to its former position and air from line 15 is switched on to line 12 so that the piston rod 10 is forced out of the cylinder 8 and the beam is swung back to the position indicated in FIGURE 1.

The setting of the stops is such that the increment of forward movement of the article during a traverse of the carriage is a factor of the width of the spray of paint where it impinges on the surface of the article and the component of movement of the carriage in the direction of movement of the article being equal to the increment of movement of the article, vertical overlapping bands of paint are sprayed on to the side of the article. The overlapping is uniform over the whole side so that a uniform coating is produced. For example in one embodiment of the invention the increment of conveyor movement per stroke of the carriage is 4 inches, and the width of the spray fan is 12 inches where it impinges on the surface of the side of the article, and a uniform triple coating is produced. Alternatively if the increment of conveyor movement is 6 inches, a uniform double coating is roduced by a spray fan 12 inches wide.

It is to be understood that although the beam-swinging means has been described as a wholly pneumatic circuit, other beam-swinging means may be employed, for example e-lectrical means, mechanical means, or electrically operated pneumatic means.

As is usual, the apparatus is normally inoperative and operation thereof is initiated by the breaking, by an article presented by the conveyor for painting, of a light beam projected from a light source 41, FIGURES 2 and 3, on to a control photocell 41a, FIGURE 3.

The beam, and carriage which runs on the beam are illustrated in greater detail in FIGURES 2 and 3. The beam, indicated at 42, is supported in a vertical plane by the pivot 7 which is mounted in brackets 43 supported from the base 36 at each side of the beam. The carriage 4 to which the spray gun 3 is connected by a linkage 44 has wheels 45 which run on the edges of the beam which are formed as rails 46 for the wheels.

The carriage 4 is formed with a slot 47 in which a drive dog 48 engages. The drive dog 48 is fixed to an endless chain 49 which runs over the sprockets 50 and 51 mounted near opposite ends of the beam and driven by a drive to the lower sprocket 51 from a motor 52 mounted on the beam 42. Power supplies to the motor are on lines 51a through a switching relay circuit 51b which is operated by an impulse on line 41b from the control photocell 4111 when the beam 01f light falling on the photocell is broken by an article to be coated. The circuit 51b starts the motor 52 when an article approaches the spray gun and the spraying of the upright side of the article facing the spray gun is then effected.

The air cylinders 28 and 29 which cushion the carriage at the ends of its strokes are mounted on the beam 42 as shown in FIGURES 2 and 3.

Atomising air, control air and coating material are supplied to the spray gun 3 by service hoses indicated at 53 in FIGURE 3 which are connected to a manifold on the gun arm 54. Supply of air and coating material is controlled in known manner by valves which are operated by the control air, which is itself controlled by cams driven from the same drive as the carriage 4. The cams are contained in a cam box mounted at the top of the beam 42 and driven from the sprocket 50. The cams operate valves which govern the feeding of control air to the valves for the atomising air and coating material and any one of a number of cams, for example four cams, can be manually selected so that the operation of the spray gun 3 is determined for different sizes of articles 1. A standard timer may also be connected to the output from the motor 52 which timer operates air valves connected to lines 16 and 17 and which operate the spool valve 14 so that control of the swinging of the beam is from the control drive and timing of the machine rather than from the two cylinders 28 and 29. In this modification however the cylinders 28 and 29 may be retained to cushion the ends of the carriage stroke or may alternatively be replaced by cushioning springs.

Means may also be provided for moving the linkage including the gun arm 54 to move the spray gun 3 in and out towards and away from the side of the article being coated to account tfOI' the widths of articles.

If desired, when .the conveyor is a very fast moving conveyor there may be two spray guns mounted side-byside on the carriage as shown diagrammatically in FIG- URE 4, with control means 56 connected to the spray guns, the arrangement being such that as the light beam is broken by the approach of an article to be painted one gun is first caused to operate, the second gun being operated through a time delay device at a predetermined time following the commencement of operation of the first gun. As the article is moved out of the range of the guns the gun first operated will be first cut off while the second gun continues to operate until the stroke of the carriage is completed when it is, in turn, out off.

The apparatus of FIGURES 1 to 3 is illustrated in greater detail in FIGURES 5 and 6. l The beam 42 is a channel-section beam and rails 46 are fixed to the outer surfaces of the two flanges 60 of the beam. The base of the beam 42 is bolted to a plate 61, FIGURE 6, forming part of a bracket 62 which is welded to a cross-piece 63 which includes end plates 64 which are bolted to face plates 65 respectively welded to trunnions 66. The trunnions 66 are mounted in split journal bearings 67 which are mounted on support plates 68.

Each of the support plates 68 is welded to the top end of a channel section vertical support 69, there being two supports 69 as shown in FIGURE 6, mounted on base plates 70 and stabilised by means of struts 71. The base plates 70 are bolted to the floor through flanges 72.

A cross-piece 73 fixed between the two base plates 70 carries brackets 74 between which a lug 75 fixed to one end of the cylinder 8 is mounted on a pivot pin 76.

The piston rod ends in a fork 77 in which there is pivotally held a lug 78 fixed to the lower end of the beam 42.

The motor 52 is held on the beam 42 by an adjustable mounting. A screw 79 extends between two brackets 80 and passes through threaded flanges 81 integral with the base plate of the motor. By turning a hand Wheel 82 fixed to the upper end of the member 79 the position of the motor can be adjusted vertically. The motor pulley 83 is connected by a V-belt 84 to a V-pu'lley 85 fixed to the input shaft of a reduction gear box 86. The output shaft of the gear box 86 has the lower sprocket 51 fixed to it. The chain 49 extends between the lower sprocket 51 and the upper sprocket 50 also mounted on the beam 42 as shown in FIGURE 3. The sprockets 50 and 51 and the 'chain 49 are omitted from FIGURES 5 and 6 0501 the sake of clarity but idler bearings 87 for'the sprocket 50 are shown in FIGURE 5, which bearings are mounted on a flange plate 88 which is adjustably mounted on the back face of the beam 42. Adjustment is by means of a bolt 89 passing through a lug 90 fixed to the beam 42, there being side guides 91 to locate the mounting for the bearing 87.

A drive dog on the chain 49 engages in the slot in the carriage 4 to cause reciprocation of the carriage up and down the beam as shown in FIGURE 3. At each corner of the carriage as shown in FIGURES 5 and 6 there are mounted three wheels, and at each corner a Wheel 92 runs on the outer face of the rail 46 while there are a pair of wheels 93 and 94 which run on the side faces of the rail 46. The wheels 93 and 94 are mounted on a support plate 95 which is fixed to the corner of the carriage 4.

The spray gun 3 of well known kind is mounted on a gun arm 96 which is fixed to a linkage including link members 97 and 98 which are pivotally interconnected and are connected to the carriage 4 by further links 99 and 100. The links 99 and 100 are pivotally mounted at their upper ends on pivots 10 1 and 102 fixed to the carriage 4.

At the bottom of the beam 42 there is welded a web plate 103 which is disposed horizontally and carries a vertical member 104 on which is mounted a cam track 105. Rollers 106 fixed to the end of the link 97 opposite the gun arm 96 bear on the cam track '105 and the track canbe so shaped as to tilt the spray gun as it ap proaches the top and bottom of its spraying traverse. It may not be necessary to tilt the gun when the upright sides of articles being coated are of rectangular form, but tilting is advantageous if the top and bottom of the sides of the article are slightly curved.

A cam surface 110, FIGURE 5, is mounted onthe carriage 4 and is so arranged as to co-operate with two cam-operated air control valves .112 and 113 respectively mounted near the top and bottom of the beam 42 beyond the limits of the top and bottom edges of the article surface being coated. Each of the control valves 112 and 113 is of well known kind having a control lever 114 carrying a roller 115 and when the cam surface on the carriage engages the roller of either of the valves the roller is depressed and the appropriate valve is operated.

The valves 1 12 and 113 are both shown diagrammatically in FIGURE 7, which is a diagram of the pneumatic circuit for operating the apparatus of FIGURES 5 and 6. An input air line 116 is connected to two air circuits, one being the circuit which supplies operating air to the spray gun 3 and the other being the circuit which supplies air to operate the spool valve 14 which controls operation of the beam swinging cylinder 8. The main air supply line 116 is connected through a filter 117, a regulator 1'18 and a lubricating device 119 of well known kind to the air line 15 which supplies air for switching through the spool valve 14. A branch line 120 of the output from the lubricator 119 is connected to a manifold indicated at 121,

being there connected to two flexible hoses .1 22 and 123 which are respectively connected to the cam operated valves 112 and 113, which valves respectively switch air under pressure to the lines 17 and 16 which are connected to the side control ports of the spool valve 14.

Control air for operating the spray gun is taken on line 124 which connects line 116 to a solenoid operated air valve 125 of well known kind. This valve 125 has electrical input leads 126 which may be wired into the control circuit of the conveyor which carries articles 1 to be coated past the spraying apparatus, the connection being such that when the conveyor stops the valve i125 closes, so cutting off the supply of control air to the spray gun 3. This ensures that spraying stops if the conveyor stops.

The outlet from the valve 125 is connected .to a bleeder air valve 127 which is itself connected by an air line 128 to a manifold 129. There the line 128 is connected to a flexible hose 130 which is connected to a cam operated valve 131 mounted in the cam box 55 of the apparatus. For the sake of clarity .the cam box 55 has been omitted from FIGURES 5 and 6, but as already described with reference to FIGURE 2 is of well known kind including timing cams, one of which is adjusted to operate the valves 131 so that air is only supplied on line 53 to the spray gun manifold at the appropriate times for switching the spray gun on and off as it traverses through each path past the surface of the article being coated.

In an alternative embodiment the spray gun operating air valve 131 may be mounted on' the carriage 4, there being a further cam surface mounted on the vertical member 104, which cam surface is engaged by the roller 132 on the valve 131 during that part of the traverse of the carraige when control air is required to the be supplied to the spray gun 3.

It will be appreciated that control air has to be switched to the spray gun a short time before the spray gun is opposite the surface being coated, and that the control air is switched off by operation of the valve 1311 as the gun is approaching the opposite side of the surface. This is true of both the upward and the downward traverse of the spray gun so that in some instances two separate cam tracks may be provided, one to control the operation of the spray gun during the upward movement of the carriage and the other to control the spray gun during the downward movement.

In the preferred embodiment where the switching of control air to the spray gun through the valve 131 is controlled by a timing cam in the cam box 55, that cam is arranged so that it makes one revolution in one complete cycle of the carriage and the cam surface is appropriately formed to switch the control air on and off at the appropriate times during the upward and downward traverse of the carriage.

By the use of apparatus as herein described painting is effected in substantially straight vertical overlapping strokes which provide a more even coating than that of prior painting apparatus in which the painting strokes are inclined across the surface of the article, and the arrangement is such as considerably to reduce the cycle overspray before and after the article as compared with the prior used apparatus thus resulting in a saving of paint.

I claim:

1. Apparatus for coating an upright surface of an article, comprising a beam supportable for pivotal movement about a horizontal .axis intermediate its ends in a vertical plane parallel to the path of a conveyor by which articles to be coated are moved in a straight path at a constant linear speed, a carriage mounted on the beam, work controlled means for reciprocating the carriage in a straight line path up and down the beam, a coating material spraying device supported on the carriage and arranged to spray coating material on to an upright surface of an article during movement of the article past the spraying device, .and beam swinging means including fluid pressure control devices fixed to the beam and operable at the end of each stroke of the carriage to swing the beam about said axis, to reciprocate said carriage and dampen the carriage movement at said end of each stroke, whereby the spraying device during successive strokes thereof is traversed along straight line paths inclined on opposite sides of a line at right angles to the direction of movement of the articles and in a direction in each path such that a component of the movement of the spray- 3 ing device always lies in the same direction as the direction of movement of an article being coated.

2. Apparatus according to claim 1, wherein the beamswinging means comprises .a change-over air cylinder housing a piston, a piston rod connecting the piston to the beam at a position adjacent to one end of the beam, compressed air supply means connected to said cylinder and pneumatic switching devices mounted at the ends of the beam and connected to the compressed air supplying means, each pneumatic switching device being operable when contacted by the carriage at the end of a stroke of the carriage to cause the compressed air supply means to switch over the supply of air to said change-over cylinder thereby causing the beam to swing about its axis.

3. Apparatus according to claim 2, including stops engageable by the beam to determine the extent of swinging movement of the beam, said stops being adjustable relative one to the other to vary the spacing therebetween according to the linear speed of the conveyor.

References Cited by the Examiner UNITED STATES PATENTS 1,835,402 12/1931 Juers 118-323 1,929,896 10/1933 Merritt et al. 118-323 1,956,220 4/1934 Johnson et al 117-1053 2,488,519 11/1949 Andrews et al. 118-2 2,588,125 3/1952 Knowland et al. 118-323 X 2,754,795 7/ 1956 Enssle 118-2 2,770,216 1 1/1956 Schock 118-323 2,777,419 1/1957 Paasche 118-2 2,840,038 6/1958 Verba 118-323 2,892,438 6/1959 Hery 118-2 2,900,950 8/1959 Peeps 118-323 X 2,925,801 2/1960 Bivens et al. 118-323 MORRIS KAPLAN, Primary Examiner.

RICHARD D. NEVIUS, Examiner.

JOHN P. MCINTOSH, Assistant Examiner. 

1. APPARATUS FOR COATING AN UPRIGHT SURFACE OF AN ARTICLE, COMPRISING A BEAM SUPPORTABLE FOR PIVOTAL MOVEMENT ABOUT A HORIZONTAL AXIS INTERMEDIATE ITS ENDS IN A VETICAL PLANE PARALLEL TO THE PATH OF A CONVEYOR BY WHICH ARTICLES TO BE COATED ARE MOVED IN A STRAIGHT PATH AT A CONSTANT LINEAR SPEED, A CARRIAGE MOUNTED ON THE BEAM, WORK CONTROLLED MEANS FOR RECIPROCATING THE CARRIAGE IN A STRAIGHT LINE PATH UP AND DOWN THE BEAM, A COATING MATERIAL SPRAYING DEVICE SUPPORTED ON THE CARRAIGE AND ARRANGED TO SPRAY COATING MATERIAL OF THE ARTICLE PAST THE OF AN ARTICLE DURING MOVEMENT OF THE ARTICLE PAST THE SPRAYING DEVICE, AND BEAM SWINGING MEANS INCLUDING FLUID PRESSURE CONTROL DEVICES FIXED TO THE BEAM AND OPERABLE AT THE END OF EACH STROKE OF THE CARRIAGE TO SWING THE BEAM ABOUT SAID AXIS, TO RECIPROCATED SAID CARRAIGE AND DAMPEN THE CARRIAGE MOVEMENET AT SAID END OF EACH STROKE WHEREBY THE SPRAYING DEVICE DURING SUCCESSIVE STROKES THEREOF THE TRAVERSED ALONG STRAIGHT LINE PATHS INCLINED ON OPPOSITE SIDES OF A LINE AT RIGHT ANGLES TO THE DIRECTION OF MOVEMENT OF THE ARTICLES AND IN A DIRECTION IN EACH PATH SUCH THAT A COMPONENT OF THE MOVEMENT OF THE SPRAYING DEVICE ALWAYS LIES IN THE SAME DIRECTION AS THE DIRECTION OF MOVEMENT OF AN ARTICLE BEING COATED. 